Apparatus for the solidification of molten sulphur

ABSTRACT

A thin layer of solidified sulphur is formed by discharging molten sulphur onto a conveyor belt supported on loosely retained rollers, and passing the belt on the rollers through a cooling zone, where the underside of the belt is cooled by cooling liquid. The rollers may be buoyant, or may be supported, to maintain the belt at a correct level relative to the level of the liquid.

Ellithorpe et a1.

[ APPARATUS FOR THE SOLEDIIFICATHON OF MOLTEN SULPHUR [73] Assignee:Vennard & lEllithorpe LttL, Calgary,

Alberta, Canada 22 Filed: Apr. 5, 1972 121 Appl. No.:24111,355

[30] Foreign Application Priority Data 1,742,194 l/1930 Bennett 62/3452,035,990 3/1936 Siegler 23/295 2,665,973 1/1954 Morningstar ct al.23/293 S 3,436,927 4/1969 Gruber 62/345 3,529,430 9/1970 Baucrlein 62/72FORElGN PATENTS OR APPLICATIONS 1,221,874 6/l960 France 23/308 5 PrimaryExaminerl lorman Yudkoff Assistant Examiner-R. T. Foster Attorney,Agent, or Firm-loel E. Siegel; Charles M. Kaplan Nov. 11,1971 Canada126653 [57] TR v {52] U S U 23/273 R 23/308 S 23/270 B A thin layer ofsolidified sulphur is formed by dis- I u 23/295 62/345 charging moltensulphur onto a conveyor belt sup [5]] Int (1 i 9/00 ported on looselyretained rollers, and passing the belt [58] i B 312 A on the rollersthrough a cooling zone, where the un- /312 5 62/72 derside of the beltis cooled by cooling liquid. The rollers may be buoyant, or may besupported, to maintain [56] References Cited the belt at a correct levelrelative to the level of the UNITED STATES PATENTS 1,396,485 11/1921White 23 312 3 9 Claims, 11 Drawing Figures /5 E L 251 4/ 4/ L/ g 1' f5/7 1 i 7 I 25 57% M O/PA-ZT 2 PATENTEB [ET 1 I 74 SHEET '4 W a APPARATUSFOR THE SULIDIFIICATIION F MULTEN SIULII-IIJIR This invention relatesgenerally to an improved method and apparatus for the cooling of moltensulphur, for example to produce solid sulphur in the form of relativelythin layer so that it can then be broken into fragments suitable forstorage and transport.

The present invention is a further development of, and presents analternative method and apparatus, to that which is specifically taughtin the applicants US. Pat. applications Ser. No. 3,558 filed Apr. 21,1970, Ser. No. 158,076 filed June 29, 1971 and Serial No. 207,909 filedDec. 14, 1971.

For many years, sulphur was reclaimed as a fine powder which presented aserious dust nuisance during storage, during handling, and duringtransportation. With increasing public consciousness of pollution, thedust clouds and surface coating arising when sulphur is handled in theform of a fine powder have become even less acceptable, and the patentapplications referred to above, and the present application, relategenerally to a process which results in the production of sulphur as amass of flakes which are commonly referred to as slates. These do notbecome airborne under any normal conditions, and thus the dust nuisancecommonly associated with sulphur is essentially eliminated. The flakesare produced by the production of a thin layer of the solidifiedsulphur, which is then broken into flakes in any convenient manner, suchas by discharge off an elevated conveyor belt.

An object of the present invention is the provision of improvedapparatus for the formation of the desired thin layer of solidifiedsulphur, which can then be broken up into flakes as required.

According to the present invention, sulphur is discharged onto a flatconveyor belt and distributed evenly on the belt, which is moved in ahorizontal direction through a cooling zone. The underside of the beltis subjected to cooling by liquid while the cooling zone is traversed bythe belt, and is supported on loosely retained rollers. The uppersurface of the molten sulphur is subjected to cooling by a current ofcool gas while the cooling zone is traversed by the belt.

The invention will now be described, by way of example, with referenceto the accompanying largely diagrammatic drawings, in which:

FIG. 1 is a sectional side elevation through a sulphur cooling andslating unit;

FIG. 2 is a transverse section taken on the line II-II of FIG. l and asviewed in the direction indicated by the arrows;

FIG. 3 is a sectional side elevation drawn to a larger scale than FIG. 1and showing only that part adjacent section line lI-II;

FIG. 4 is a plan view of that part of the unit shown in FIG. 3;

FIGS. 5 is a sectional transverse elevation of the right-hand side orend only ofa roller shown in FIG. 2;

FIG. 6 is a transverse section taken on the line VIVI of FIG. 1 asviewed in the direction indicated by the arrows;

FIG. 7 is a transverse sectional view similar to FIG. 2 but showing analternative embodiment of the inventlon;

FIG. 8 is a plan view of the part. of the unit shown in FIG. 7; and

FIGS. 9, l0 and 11 are side elevations, partly in section, of threealternative forms for rollers shown in the earlier Figures.

Referring first to FIG. ll, molten sulphur is fed to a cooling towerdesignated generally at 1 at an upper level, and flows downwardlythrough the tower in sinuous flow over a number of staggered horizontalfloors or baffles 3. Cooling air is blown into the tower by a fan (notshown), and the molten but partly cooled sulphur is collected in a tankbottom of the tower 1. From there, it is pumped or is allowed to flow bygravity through a steam jacketed line 5 under the control of a valve 7to the slating unit proper.

The slating unit includes an endless conveyor belt 9 having a length of2l 2 feet and a width of 60 inches, the belt being provided on itsworking face with upright flanges 11 extending respectively along thetwo edges of the belt and having a height of one-half inch. This isshown clearly in FIG. 5. The belt 9 at its forward end, i.e., near thetower 1, extends round a large roller 13 and then, in the direction oftravel indicated by the arrow 15 in the various figures, slopesdownwardly for a short distance at 9A before extending horizontally at98, supported on rollers 17. The extent of the horizontal portion 98 is60 feet, and beyond the last of the rollers 17 the belt is allowed tosag to form the concave section 9C, having a horizontal extent of 20feet, before passing under a large roller 19 and above a supportingroller 21 to extend at an upward inclination at 9D to pass over a drivenroller 23. After passing over that roller 23, the belt returns underrollers 23, 21 and 17 to the roller 13.

A cooling pan 25 in the form; of an open-topped trough containingcooling water contains also the rollers 17, the lower part of roller 13,and the parts 98 and 9C of the conveyor belt 9. The water level in thecooling pan 25 is maintained substantially constant by suitable controlmeans, not shown, and the temperature of the water in the cooling pan iskept at a desired level by the continuous extraction of a suitable flowof the water through a pipe 27 leading to a heat exchanger 29, fromwhich the cooled water returns through pipe 31 to the pan 25. Thedetails and components of the devices needed to control both temperatureand water level do not form part of the present invention, and will beclear to those skilled in the relevant art.

Disposed above the horizontal part 98 of the conveyor belt are threefans 33 enclosed in hoods 35 and provided with suitable air directinglouvres at their air outlets. As indicated by the arrows 37 associatedwith these fans, each fan directs cooling air downwardly at aninclination in the direction of travel of belt part 98, and thearrangement is such that the air so discharged is effective both to coolthe liquid sulphur which as described below, is on the surface of beltpart 98, and to distribute that molten sulphur evenly from edge to edgeover the belt surface. Although fans are shown, it would clearly be asuitable alternative to use a remote fan supplying air to ducts havingoutlet ports louvred and directed as described above.

Disposed beyond the roller 23 is a further belt conveyor 39 passing overtroughing idler rollers 41 and arranged to collect material dischargedby the belt 9 over the roller 23.

Referring now to FIGS. 2 through 5, these show in detail the arrangementof the belt part 913 and of the rollers 17 in the cooling pan 25. Eachof the rollers 17 is formed from a 72 inch length of 3 inch Schedule 40P.V.C. pipe. Such pipe has an internal diameter of three inches and anoutside diameter ofthree and a half inches, and the two ends of the pipelength forming a roller are closed by plugs 43. It has been founddesirable to fill the part of the pipe between the plugs with aclosed-pore plastic material 45, since otherwise the pressure built-upin the pipe at its elevated operating temperatures may blow the plugsout of the end of the pipe. It is, of course, possible as an alternativeto use evacuated pipe lengths, or provide other pressure accommodatingmeans to avoid this difficulty.

Each roller 17 is buoyant, its overall specific gravity being 0.32 inthe example given. Its length is such, compared with the width of thepan 25, that it can rotate freely but is capable of only very limitedendwise movement. At the same time, since each roller is considerablylonger than the width of the belt 9, the belt is substantially evenlyplaced on the roller at all times. The rollers 17 are kept at a desiredspacing and in parallel arrangement, extending transverse to thedirection of travel of the belt 9, by upright brackets 47 welded to thevertical side walls of pan 25. The brackets are arranged in pairs, onepair for each roller, and along each side of the pan 25 the brackets arespaced apart at a pitch of 12 inches. Since the brackets extend inwardlyto a point close to the belt 9, and since they extend upwardly nearly tothe top of the pan 25, they serve both to hold the rollers 17 inparallel spaced relationship and to centralize both the part 9B of belt9 and the lower return run of that belt, in the pan 25.

In use of the apparatus described above, liquid sulphur is distributedevenly by pipe 5 onto part 9A of the belt 9. Its sideward flow off thebelt is prevented by the two flanges 11. The part 9B of the belt issupported on the rollers 17, and in any particular installation theseflotation rollers are designed to support the weight of the sulphurcoated belt so that the rollers and the lower part of the belt part 98are submerged in the water in the pan 25 (the water level is indicatedat 49 in FIG. 5) but the water is excluded from the top of the belt part9B by the flanges 11. This requires a careful analysis of all therelevant operating conditions and a suitable design both of the rollersand their distribution along the belt part 98. Thus, it is necessary toconsider the belt weight per foot run without any load; the sulphur loadto be expected, e.g., 8 to 10 pounds per foot run; and the buoyancy andthe number of spacing of the rollers 17. Further, excessive variationsin water level and excessive turbulence in the water is to be avoided,and the brackets 47 tend to dampen ripples and waves in the water in thepan.

While passing along with the belt part 98, the sulphur 49 is subjectedto preliminary cooling by the air discharged by the fans 33, and thisair discharge also tends to improve the even distribution of the coolingmolten sulphur. The water in the water pan 25 cools the rollers 17 andthe belt part 9B. The belt typically is travelling at 60 feet perminute, so that the air cooling lasts for about 1 minute, at the end ofwhich time the belt 9 passes over the last of the rollers 17 and, underthe weight of itself and its load, dips down so that the belt isgradually submerged into the cooling water. Belt tension, and thebuoyancy of the belt and the sulphur,

keep the belt supported in the cooling water for a distance of 20 feet,after which it emerges as a relatively gentle inclination and, as beltsection 9D, inclines towards roller 23.

During the period of about twenty seconds while the belt is passing upthe incline at section 9D, water drains from the sulphur on the belt andfurther water evaporates from the partly solidified sulphur before it isdropped off the belt 9, as it passes over roller 23, onto the conveyor39. Conveyor 39 conveys the sulphur, now broken into small plate-likepieces or slates, to a suitable storage pile.

It will be appreciated by those skilled in the art that considerablecare is needed in putting the invention into practice. Thus, forexample, the cooling water circulated through the pan 25 must becarefully controlled. Merely by way of example, in the arrangement whichhas been described generally above, it was found that for a group of sixsuch units cooling water was circulated at a rate which varied between250 to 600 US. gallons per minute, the system then working to produceslated sulphur at a rate of 15 long tons per unit, equal to long tonsper hour from the group of units. In that example, the water coolingsystem had a cooling capacity of 1,015,000 k Calories, assuming anaverage liquid sulphur system input temperature of about 250F. For aninstallation in countries such as Canada, it is important to take intoaccount the ambient air temperature, which may vary over the range 50F.to +l30F. In a practical installation, a sophisticated control system tointegrate all the relevant variables would be used, but such systems arewell known in the art and do not in themselves form part of the presentinvention, and therefore are not described herein.

The apparatus described above in connection with FIGS. 1 though 6 hasbeen found to overcome a number of difficulties experienced with theearlier proposals by the present applicant. In the original apparatuscontemplated by the applicant, the belt carrying molten sulphur wasarranged to slide over metal guide pans which supported the belt on thesurface of the water and this presented three problems:

a. the amount of power required to drag the belt with a sliding actionover the fixed pans;

b. if the water level in pan 26 became low, the belt would rise from thewater and, no longer being cooled, becomes excessively hot, sointerfering with the desired cooling of the sulphur; and

c. the rubbing of the belt on the fixed pans caused excessive wear ofthe belt.

By the use of rollers to support the section 98 of the belt evenly atthe proper position relative to the surface of the cooling water, evencooling of the belt was assured, and in addition, the friction involvedwas considerably reduced. As a result of the replacement of a slidingmotion between the belt and its support with a rolling motion, wear onthe belt was significantly reduced.

In the arrangement of FIGS. 1 through 6, buoyant rollers 17 were used,and this had the added advantage that no exact control of the waterlevel in the pan 25 was required. However, many of the advantages of theembodiment of FIGS. 1 through 6 can be obtained with the arrangementshown in FIGS. 7 and 8. In that arrangement, the buoyant rollers 17 ofthe earlier embodiment are replaced with rollers 117 which are notbuoyant, and can be made of any material suited to their operatingconditions. In this arrangement, the pan 25 is provided as before withbrackets 47 which maintain the rollers 117 in the desired spacedparallel relationship, but additionally the floor of the pan 25 isprovided with longitudinally extending support strips 119 extendingrespectively along side parts of the pan floor, and of such height that,when the rollers I17 rest on the strips 119 and the belt part 98 restson the rollers 117, the top surface of the belt part 9B is at apredetermined level in the pan 25. It is of course necessary, with thisarrangement, to provide means for the accurate control of the waterlevel 121 in pan 25, but since this is, in any case, a requirement inthe earlier proposals by the ap plicant, the embodiment of FIGS. 7 and 3provides reduced power requirements and reduced wear without any furthercomplication in the apparatus.

FIGS. 9, 10 and 11 show alternative forms for the rollers on which thebelt 9 travels. In each case the roller 17 is formed from a tube havinga nominal bore of 3 inches and an outside diameter of 3 /2 inches. Ateach end each roller is provided with an encircling sleeve having alength of 8 inches and an overall diameter of 4 /2 inches.

In the embodiment shown in FIG. 9, this sleeve 17A is a plain sleeve asshown, and serves as a bearing surface which engages the brackets 47.

In the embodiment shown in FIG. It], this sleeve 17B tapers in thicknessendwise of the roller 17, being of lesser diameter towards the centre ofthe roller.

The sleeve 17C shown in FIG. 11 is, in effect, the sleeve 178 butsectionalised by circumferential cuts 17X into a number of spaced sleeveparts.

The objective of using such modified ends on the rollers 17 iscompensate for belt stretching and belt deformation in use. Further, ittends to improve the evenness of liquid sulphur distribution over thefull width of the cooling belt. As mentioned above, by the use ofreplaceable sleeves, wear on the actual rollers can be eliminated.

It will be seen that by the apparatus of the present invention, theapplicants have improved factors such as the performance and the rate ofwear in the apparatus. It is found that a more consistent output can beobtained when, as described above, the sulphur is cooled on ahorizontally moving belt which is subjected to water cooling on itsunderside while the sulphur is cooled by air directed downwardly on itsupper surface.

We claim:

1. Apparatus for forming a thin layer of solidified sulphur whichcomprises:

a. a flat conveyor belt;

b. means for discharging molten sulphur onto said s belt;

c. means arranged to distribute the molten sulphur evenly on said belt;

d. driving means arranged to produce continuous lengthwise movement ofsaid belt;

e. vertically loosely retained roller means arranged to support saidbelt for movement in a horizontal direction through a cooling zone; and

f. cooling means for subjecting an underside of said belt to cooling bya liquid while the cooling zone is traversed.

2. Apparatus as claimed in claim I further comprising means forsubmerging said belt in cooling liquid after leaving said cooling zonewith its cooled sulphur.

3. Apparatus as claimed in claim 1, further comprising a container forcooling liquid in said cooling zone, means for guiding said belt in ahorizontal direction through said container and means for inhibitingcooling liquid from flowing onto the molten sulphur.

4. Apparatus as claimed in claim 1, wherein said inhibiting meanscomprise upwardly extending parts at each side edge of said belt.

5. Apparatus as claimed in claim 1, further comprising a container forcooling liquid in said cooling zone and means for guiding said beltthrough said container, said loosely retained roller means comprisingbuoyant rollers free to float in the cooling liquid so that said belt ismaintained at such a level relative to said liquid as to prevent coolingliquid from flowing onto the molten sulphur.

6. Apparatus as claimed in claim 5, wherein stops are provided in saidcontainer to limit movement of each of said rollers by action of thebelt and to maintain the rollers in spaced parallel positions.

7. Apparatus as claimed in claim 1, wherein each of said rollerscomprises a cylindrical shell formed of a suitable plastics material andfilled with foamed plastics material.

8. Apparatus as claimed in claim 1, further comprising a container forcooling liquid in said cooling zone, means for guiding said belt throughsaid container and means for supporting said loosely retained rollermeans so as to maintain said belt at a fixed level in said trough,whereby said belt is maintained at such a level relative to said liquidas to prevent said cooling liquid from flowing onto the molten sulphur.

9. Apparatus as claimed in claim 1, wherein means are provided in saidcooling zone for discharging a flow of cooling gas onto the uppersurface of the molten sulphur.

1. APPARATUS FOR FORMING A THIN LAYER OF SOLIDIFIED SULPHUR WHICHCOMPRISES: A. A FLAT CONVEYOR BELT, B. MEANS FOR DISCHARGING MOLTENSULPHUR ONTO SAID BELT, C. MEANS ARRANGED TO DISTRIBUTE E THE MOLTENSULPHUR EVENLY ON SAID BELT, D. DRIVING MEANS ARRANGED TO PRODUCECONTINUOUS LENGTHWISE MOVEMENT OF SAID BELT,
 2. Apparatus as claimed inclaim 1 further comprising means for submerging said belt in coolingliquid after leaving said cooling zone with its cooled sulphur. 2.VERTICALLY LOOSELY RETAINED ROLLER MEANS ARRANGED TO SUPPORT ASID BELTFOR MOVEMENT IN A HORIZONTAL DIRECTION THROUGH A COOLING zONE, AND F.COOLING MEANS FOR SUBJECTING AN UNDERSIDE OF SAID BELT TO COOLING BY ALIQUID WHILE THE COOLING ZONE IS TRAVERSED.
 3. Apparatus as claimed inclaim 1, further comprising a container for cooling liquid in saidcooling zone, means for guiding said belt in a horizontal directionthrough said container and means for inhibiting cooling liquid fromflowing onto the molten sulphur.
 4. Apparatus as claimed in claim 1,wherein said inhibiting means comprise upwardly extending parts at eachside edge of said belt.
 5. Apparatus as claimed in claim 1, furthercomprising a container for cooling liquid in said cooling zone and meansfor guiding said belt through said container, said loosely retainedroller means comprising buoyant rollers free to float in the coolingliquid so that said belt is maintained at such a level relative to saidliquid as to prevent cooling liquid from flowing onto the moltensulphur.
 6. Apparatus as claimed in claim 5, wherein stops are providedin said container to limit movement of each of said rollers by action ofthe belt and to maintain the rollers in spaced parallel positions. 7.Apparatus as claimed in claim 1, wherein each of said rollers comprisesa cylindrical shell formed of a suitable plastics material and filledwith foamed plastics material.
 8. Apparatus as claimed in claim 1,further comprising a container for cooling liquid in said cooling zone,means for guiding said belt through said container and means forsupporting said loosely retained roller means so as to maintain saidbelt at a fixed level in said trough, whereby said belt is maintained atsuch a level relative to said liquid as to prevent said cooling liquidfrom flowing onto the molten sulphur.
 9. Apparatus as claimed in claim1, wherein means are provided in said cooling Zone for discharging aflow of cooling gas onto the upper surface of the molten sulphur.